Automotive Engine Coolants: A Review of Their Requirements and Methods of Evaluation

A brief review of early automobiles shows the development of the engine cooling system, and some of the associated problems with these early cars are discussed.

A liquid is commonly used to transfer heat from an operating automobile engine to a radiator where the heat can be dissipated to the air. In order that the liquid perform effectively, it must have the appropriate chemical and physical properties. Of foremost consideration is the capability of the fluid to transfer heat over a wide range of operating conditions. In addition, the fluid must be stable, must not freeze when not in use or boil during or after engine operation, and must not cause or allow excessive corrosion of the parts it contacts.

To determine how well the cooling system is capable of performing its function, it is necessary to perform a variety of tests to evaluate the operational characteristics of component parts, the properties of the coolant fluid and its long-range stability, and the capability of the fluid to minimize corrosion of all materials. Tests range from the shorttime laboratory test to the longer and more comprehensive field test. Operating conditions are often difficult to simulate in the laboratory, and the test tends to be restrictive. Field tests are usually more definitive but can be difficult to control. However, the end result of an effective development program over a number of years has been a cooling system that has provided good durable service.